The invention relates to a multi-layered foil body, a security element with at least one foil body, a security document with at least one foil body, a transfer foil with at least one foil body as well as a method for producing a multi-layered foil body.
WO 2009/043482 A1 describes a security element for the identification of a security document such as a banknote. The security element has a multi-layered foil body with a PDLC layer which reversibly changes from a scattering state into a transparent state when an electric field is applied (PDLC=Polymer Dispersed Liquid Crystal). This change in transmission is controlled by a piezoelectric energy source of the security element: when a piezoelectric material of the energy source is bent, an electric voltage is produced which is applied to electrodes on both sides of the PDLC layer in order to thus generate the electric field.
The variations in optical appearance that can be produced by such a security element are often difficult to see under unfavorable light conditions and not conspicuous enough for the “man on the street”. The level of protection against forgery that can be achieved therewith is thus relatively limited.
WO 2008/083921 Al relates to a value or security document with an optical transmitter. In addition to a visually perceptible signal, a visually imperceptible signal is to be emitted.
For this, in one embodiment there is a monochrome liquid crystal display, to which an infrared filter is connected upstream. In this embodiment, a reflector is provided, in front of which a polarizer is arranged. On a substrate with a transparent back electrode there is a liquid crystalline layer, on which, for its part, there is a structured electrode, and the structured electrode comprises picture elements (pixels).
In a modification of this embodiment, a colored representation is additionally made possible. Each picture element (pixel) comprises three subpixels for respective color components, blue, green and red. A further subpixel serves to emit a machine-readable signal in a visually imperceptible spectral range. The subpixels comprise partial electrodes, in front of which there are corresponding color filters that define the properties of the subpixel.
DE 10 2007 048 102 Al describes a security element with a piezoelectric energy source that controls a change layer.